Tips do not count as part of minimum wage. However, you may need to pay tax on any tips you receive.
The Act does not cover voluntary work for a registered charity, and does not apply in all circumstances. However, unless undertaking work experience specifically as part of your course, you should be paid the minimum wage. As a general rule, vacancies advertised through your Careers Service pay at least the higher rate (21+ years).
You can find more information on the DirectGov website, a government website giving advice to employees about a range of employment and work-related matters, including the national minimum wage or via the Pay and Work Rights helpline.